Many loose-leaf binding mechanisms are known in the art. For example, a traditional binder mechanism is shown in DAWSON, U.S. Pat. No. 2,041,168, wherein semicircular ring members have inner ends joined to an overcenter mechanism of a spine to which a binder cover is attached. Other overcenter loose-leaf binder mechanisms are disclosed in SCHADE, U.S. Pat. No 2,311,090, EMMER, U.S. Pat. No. 2,511,153, and COHEN, U.S. Pat. No. 4,552,478. A loose-leaf binder with a spine including cam closure rather than an overcenter closure is shown in JOHNSON, U.S. Pat. No. 3,205,895. In all of these binder mechanisms, the ring members are movable between open positions wherein their outer free ends are spaced to receive loose-leaf paper, dividers, etc., and closed positions wherein the corresponding free ends of the ring members are juxtaposed to form closed coaxial rings with the free ring member ends disposed substantially in a common plane containing the common axis of the closed rings and referred to herein as the central plane of the closed rings. The spine has a transverse cross-section whose major dimension is transverse to this central plane of the closed rings such that the spine reduces the effective ring circumference available to contain loose-leaf paper, dividers, and the like, to substantially less than 360 degrees.
Other binder constructions, such as those disclosed in V. E. CARDELLINI, U.S. Pat. Nos. 4,349,289, 4,355,916, and 4,441,834 have binder rings mounted on essentially flat spine members whose major dimension (width) is disposed substantially in the central plane of the closed binder rings, whereby substantially the full 360 degree circumference of the rings is available to contain loose-leaf papers, dividers and the like. The spine members of these latter binder constructions, however, are joined by a complex mechanism for opening and closing the rings to insert or remove papers. Published International application PC/BR81/00003 (International Publication Number WO/ 8200114) discloses a binder construction having an essentially flat spine disposed substantially in the central plane of the closed binder rings and comprising spine members hingeably joined to one another, whereby the binder ring members are rotatable between their open and closed positions. A removable channel member straddles the spine members to lock the binder rings closed. A distinct disadvantage of all of the latter binder constructions with hinged binder members is that each spine member and its ring members are integrally formed from flat sheet stock. This results in a spine member with relatively thin wide ring members extending from an edge of the spine member which will not rreceive standard multi-hole loose-leaf paper. Moreover, the spine hinge connections are between the binder ring members and not the spine members directly and are quite loose.
Therefore, there is a need for a simple, easy to manufacture ring binder which allows papers and covers to extend essentially 360 degrees therefrom for ease of use and removal of the papers and the covers without a large number of complex parts which may become broken.